The present invention relates to a seat belt buckle. In particular, the present invention relates to a seat belt buckle including a sensor for sensing when the buckle is in a latched condition.
A seat belt system for restraining a vehicle occupant typically includes seat belt webbing, a lockable element on the webbing, and a seat belt buckle. The lockable element on the webbing is inserted in the buckle when the webbing has been placed about a vehicle occupant. A latch mechanism in the buckle interlocks with the lockable element to secure the webbing about the occupant. Such a seat belt system may also include a sensor for indicating whether or not the lockable element is locked in the buckle.
In accordance with the present invention, an apparatus comprises a lockable element and a buckle for receiving and locking the lockable element in the buckle. The buckle comprises a base defining a passage into which the lockable element is insertable in a first direction, and a latch moveable to lock the lockable element against movement in the passage.
The buckle also includes a sensor which provides an output signal, the magnitude of which is dependent upon the flux density of a magnetic field acting on the sensor. A magnet is movable from a first position to a second position when the lockable element is inserted into the buckle. The magnet creates a magnetic field of a first flux density that acts on the sensor to cause the sensor to provide a first output signal when the magnet is in the first position. The magnet creates a magnetic field of a second flux density, greater than the first flux density, when the magnet is in the second position to cause the sensor to provide a second output signal greater than the first output signal. The magnet has an interference fit with one of the lockable element and the buckle.